1. Field of the Invention
This invention relates to network systems, and more particularly to discovery and configuration of devices attached to a fabric in a storage network.
2. Description of the Related Art
Storage area networks, also referred to as SANs, are dedicated networks that connect one or more systems to storage devices and subsystems. Today, fibre channel is one of the leading technologies for SANs. In general, fibre channel encompasses three networking topologies: point-to-point, loop, and fabric. In a point-to-point topology, a fibre channel host adapter in a system is typically connected to a single fibre channel storage subsystem. In a fibre channel loop network, also called an arbitrated loop, the loop is constructed by connecting devices together in a single logical ring. Loops can be constructed by connecting devices through a fibre channel hub in a star-wired topology or by connecting them together in a connected physical loop from device to device. In a fibre channel fabric topology, the storage networks are constructed with network switches. A fabric can be composed of a single switch or multiple switches. Ports on fabric networks connect devices to switches on low-latency, point-to-point connections.
The devices connected in the loop and fabric topologies may be referred to as “network nodes” and may be any entity that is able to send or receive transmissions in a fibre channel network. For example, a network node may be a computer system, a storage device/subsystem, a storage router/bridge that connects SCSI equipment, a printer, a scanner, or any other equipment, such as data capture equipment. The ANSI X3.272-1996 specification entitled “FC-AL, Fibre Channel Arbitrated Loop” and the ANSI X3.T11 Project 1133-D specification entitled “FC-AL-2, Fibre Channel Arbitrated Loop” describe examples of fibre channel loop topologies in further detail. The ANSI X3.T11 Project 959-D specification entitled “FC-SW Fibre Channel Switch Fabric” describes an example of a fibre channel fabric in further detail. Note that the most recent versions of these and related specifications may be obtained from the T11 technical committee of the National Committee for Information Technology Standards (NCITS).
For point-to-point topologies and loop topologies, device drivers executing on a host computer may perform device discovery at host boot-up to determine locally connected devices. The discovered devices are configured to be accessible to applications running on the host by creating a node for each device within the host. These types of nodes are referred to as operating system device nodes. Each node functions as an internal (to the host) representation of an attached device and provides a communication path to the device. For fabric topologies, discovering fabric devices and associated paths available to the host computer as part of the boot-up process may not be feasible because of the number of devices capable of being attached to the fabric. In addition, there may be multiple paths from a host computer to a particular device in the fabric.